Most of conventional automatic foldable umbrellas are threefold or less as shown in FIG. 1. This is because the restoring spring (A) seated between a first main stretcher (B) and a first secondary stretcher (C) can not put a strong pulling force on the outermost rib of a fourfold collapsible umbrella. The position of the restoring spring makes the spring unable to exert sufficient forces to pull back umbrella stretchers when collapsing a fourfold collapsible umbrella. Thus the conventional umbrella structure is only suitable for a threefold or less collapsible umbrella. An automatic fourfold collapsible umbrella has not yet been found.
In view of the problem, the object of the present invention is to provide a collapsing mechanism used in an automatic fourfold collapsible umbrella that makes use of an innovative mechanism to enable the stretchers of an opened fourfold umbrella to be smoothly pulled back to a retracted position, accomplishing the work that a prior art mechanism can not do. Now the features and advantages of the present invention will be described in detail with reference to the accompanying drawings.